Are all microfilters created equal

I have broadband installed and this generally has worked well.

Recently I have noticed a lot of interference on my phones which seems
to be reduced if I disconnect my router which suggests that noise from
the network side of my filters is getting across the the voice side
and presumably vice versa.

So my next step to improve my connection reliability is to change the
microfilter. The question is; is there any difference between the
different manufacturers if microfilters and if so which ones are
recommended?



news@jbrand.clara.co.uk

(E-Mail Removed) wrote:
> I have broadband installed and this generally has worked well.
>
> Recently I have noticed a lot of interference on my phones which seems
> to be reduced if I disconnect my router which suggests that noise from
> the network side of my filters is getting across the the voice side
> and presumably vice versa.
>
> So my next step to improve my connection reliability is to change the
> microfilter. The question is; is there any difference between the
> different manufacturers if microfilters and if so which ones are
> recommended?

Yes there is.
And ones costing a pound can be better than ones costing a tenner.
http://clarity.it/ (amongst others) have a filter which plugs into the
BT master socket, so that it has a filtered voice output, and needs no
further filtering, and is generally held to be of good quality.

(E-Mail Removed) wrote:

>I have broadband installed and this generally has worked well.
>
>Recently I have noticed a lot of interference on my phones which seems
>to be reduced if I disconnect my router which suggests that noise from
>the network side of my filters is getting across the the voice side
>and presumably vice versa.

You only noticed recently or you have noticed a change that happened
recently?

You microfilter is unlikely to have changed its performance so if something
changed it probably isn't the microfilter.

If you have changed nothing and it is a new problem then I would suspect a
wiring fault. A dirty or corroded connection on the line can work like a
demodulator turning some of the high frequency ADSL signal into audio
frequencies which will pass through the microfilter and be heard as a hiss
on the telephone. Such problems are often intermittent, sometimes the high
voltage ringing from an incoming call will clear the problem for a while,
sometimes the problem will be worse in damp weather.

The problem is yours if it is your side of the master socket and BT's
otherwise.

Do what you can to make sure it is not your problem, try a different
filter, try a different phone, plug the filter directly into your master
socket to bypass any extension wiring. Check the back of the master socket
is clean and dry.

A friend had this problem for months. It took 3 visits from BT engineers
before they did something in a green box a couple of streets away which
completely cured it.

The vedry best are available from a few sources including Adslnation. Take a
look here to see why.

http://www.adslnation.co.uk/support/filters.php

I have just replaced my entire internal wiring and sockets after the BT
master and have seen a dramatic improvement in the BB quality as well as the
speech. Make sure you use genuine twisted pair cable and not the crap sold
by the sheds.

Peter Crosland

On Wed, 29 Sep 2004 13:48:01 +0100, nospam <(E-Mail Removed)>
wrote:

>(E-Mail Removed) wrote:
>
>>I have broadband installed and this generally has worked well.
>>
>>Recently I have noticed a lot of interference on my phones which seems
>>to be reduced if I disconnect my router which suggests that noise from
>>the network side of my filters is getting across to the voice side
>>and presumably vice versa.
>
>You only noticed recently or you have noticed a change that happened
>recently?

It has degraded recently.

>You microfilter is unlikely to have changed its performance so if something
>changed it probably isn't the microfilter.

I also think it unlikely as the microfilter is really little more than
a low pass filter. But if the connection is borderline then I want to
give myself the best chance possible.

>If you have changed nothing and it is a new problem then I would suspect a
>wiring fault. A dirty or corroded connection on the line can work like a
>demodulator turning some of the high frequency ADSL signal into audio
>frequencies which will pass through the microfilter and be heard as a hiss
>on the telephone. Such problems are often intermittent, sometimes the high
>voltage ringing from an incoming call will clear the problem for a while,
>sometimes the problem will be worse in damp weather.

That actually sounds quite likely. I had a damp weather related
problem some years ago which turned out to be the waterproofing on the
junction box at the telegraph pole outside but that was much more
obvious. This time BT have said they can detect no fault and will
charge me to visit if they can't find a fault, which doesn't sound
like a good idea with an intermittent fault. But it may be a problem
that becomes more prevalent as we move into autumn.

>Do what you can to make sure it is not your problem, try a different
>filter, try a different phone, plug the filter directly into your master
>socket to bypass any extension wiring. Check the back of the master socket
>is clean and dry.

I've already tested at the master socket and even rewired the
connections from the master to my extensions but you have given me
another idea. Presumaby the router will spit out high requency noise
while it is attempting to negotiate a conection so if I connect just
the router and a phone to a PABX (just by chance I happen to have
several to hand) I shouldn't hear any interference

i.e. this is noisy

BT----MasterSocket----Filter------router
|
+---------phone

so if the fault is in the Filter or router this should also be noisy;

PABX-------Filter------router
|
+---------phone

If there's no noise there then presumably my router and Filter are
good and your theory about the HF demodulation is true and it is
somewhere on BT's side (or at the master socket)

>A friend had this problem for months. It took 3 visits from BT engineers
>before they did something in a green box a couple of streets away which
>completely cured it.

Sounds about right for BT's response times!

Thanks for the feedback.

(E-Mail Removed) wrote:

>I've already tested at the master socket and even rewired the
>connections from the master to my extensions but you have given me
>another idea. Presumaby the router will spit out high requency noise
>while it is attempting to negotiate a conection so if I connect just
>the router and a phone to a PABX (just by chance I happen to have
>several to hand) I shouldn't hear any interference

> If there's no noise there then presumably my router and Filter are
>good and your theory about the HF demodulation is true and it is
>somewhere on BT's side (or at the master socket)

I dont kow which end of the link an ADSL connection is initiated from so
the router might just sit there. Only if you hear some noise would anything
be proved.

>>A friend had this problem for months. It took 3 visits from BT engineers
>>before they did something in a green box a couple of streets away which
>>completely cured it.
>
>Sounds about right for BT's response times!

The BT engineers were pretty good, it is a hard problem for them to pin
down and they didn't give up.

Make sure you use genuine twisted pair cable and not the crap sold
> by the sheds.

The cable you need is to BT CW1308 specification.